Edge sealed folded membrane

ABSTRACT

A semipermeable membrane is folded to form a stack of accordian pleats of which the edges are sealed to and within a housing that provides ports for flow of blood through channels formed on one side of the membrane and provides ports for flow of a dialysate through channels formed on the other side of the membrane. End edges of the folded membrane are sealed by a unique end fold sealer plate that positions the end edges of the membrane for encapsulation within a solidifiable liquid and also blocks passage of the sealing material into the liquid flow ports formed in the sides of the case. The case is formed with enlarged end portions that facilitate the flow of the solidifiable liquid sealer material for improved encapsulation of side edges of the stack of membrane pleats. The case is made in two mating sections in a configuration readily adapted to vacuum forming. The parts are arranged so that they may be assembled in a substantially dry form and substantially all of the solidifiable liquid sealant may be injected into the case after all parts are assembled. Thus, the edge sealing encapsulation of side and end edges is performed upon the positioned and assembled parts.

United States Patent [191 Markley Feb. 4, 1975 EDGE SEALED FOLDED MEMBRANE [75] Inventor: Finley W. Markley, Tustin, Calif.

[73] Assignee: Galen Laboratories, Inc., Santa Ana,

Calif.

[22] Filed: June 25, 1973 [21] Appl. No.: 373,160

[52] US. Cl 210/321, 210/493, 264/257 [51] Int. Cl B0ld 31/00 [58] Field of Search 210/321, 493; 264/257, 264/286 [56] References Cited UNITED STATES PATENTS 3,494,466 2/1970 Rose et al. 210/493 X 3,522,885 8/1970 Lavender et al 210/321 3,612,281 8/1971 Leonard 210/321 3,757,955 9/1973 Leonard 210/493 X 3,780,870 12/1973 Esmundu 210/493 X 3,788,482 1/1974 Markley 210/493 X Primary Examiner-Frank A. Spear, Jr. Attorney, Agent, or Firm-Gausewitz, Carr & Rothenberg [57] ABSTRACT A semipermeable membrane is folded to form a stack of accordian pleats of which the edges are sealed to and within a housing that provides ports for flow of blood through channels formed on one side of the membrane and provides ports for flow of a dialysate through channels formed on the other side of the membrane. End edges of the folded membrane are sealed by a unique end fold sealer plate that positions the end edges of the membrane for encapsulation within a solidifiable liquid and also blocks passage of the sealing material into the liquid flow ports formed in the sides of the case. The case is formed with enlarged end portions that facilitate the flow of the solidifiable liquid sealer material for improved encapsulation of side edges of the stack of membrane pleats. The case is made in two mating sections in a configuration readily adapted to vacuum forming. The parts are arranged so that they may be assembled in a substantially dry form and substantially all of the solidifiable liquid sealant may be injected into the case after all parts are assembled. Thus, the edge sealing encapsulation of side and end edges is performed upon the positioned and assembled parts.

28 Claims, 18 Drawing Figures PAHNTED FEB 4 I975 sum 1 or e 1 EDGE SEALED FOLDED MEMBRANE The present invention is an improvement on the invention disclosed in my copending patent application for A Folded Membrane Dialyzer, Ser. No. 233,528

now U.S. Pat. No. 3,788,482.

BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates to methods and apparatus for flow of fluids through common wall conduits and more particularly concerns methods and apparatus for juxtaposed flow of fluids separated by a folded membrane.

2. Description of Prior Art Although experimental drug and diet treatments for persons having damaged or failed kidneys have recently been suggested, the many thousands of persons suffering from chronic kidney failure still require either artiflcal blood purification or the drastic procedure of kidney transplant. One method of artificial blood purification, hemodialysis, involves counterflow of juxtaposed blood and a dialysate, separated by a semipermeable membrane. Hemodialysis is, at present, most commonly performed in a hospital under supervision of trained personel and present systems require complex, expensive equipment and facilities and, at least in part because of the great expense, are not readily available or accessible. These systems are em ployed for periodic treatment of any one patient. Thus, during periods between treatments, blood impurities increase in concentration and the resulting ill feeling builds up until the next treatment. Further, the treatment itself is time consuming and painful, at least in part, because of the necessity of connection and disconnection of the patientss blood supply to the external apparatus.

In attempts to overcome disadvantages, complexities and expense of prior hemodialysis treatment systems, various types of simplified portable and small-size dialysis systems have been suggested.

Among these efforts have been those described in my prior U.S. Pat. Nos. 3,522,885 and 3,565,258. These parallel-flow hemodialyzers are designed to operate without use of an external blood pump and to employ inexpensive, readily available materials so that the unit may be discarded after each use. A major drawback of the hemodialyzer of these prior patents resides in the use of a relative expensive, in the preferred thickness, flattened cellophane tube stacked in a case for separating blood from the juxtaposed dialysate. The assemblies employing such tubes are expensive, complex and difficult to fabricate.

Among the many dialyzers employing sheet membrane rather than tubes, are those described in U.S. Pat. Nos. 3,396,849 and 3,442,388. However, these require complex and costly support arrangements for the membrane as in U.S. Pat. Nos. 3,396,849 or a corrugated support member to hold a membrane that is made in a corrugated form as in U.S. Pat. No. 3,442,388. Adhesive bonding of the membrane edges to a case is a significant problem in the latter arrangement since materials used internally of the dialyzer that may be in contact with the blood must be chosen with regard to reaction with the blood.

In my copending application, Ser. No. 233,528, U.S. Pat. No. 3,788,482 the disclosure of which is fully incorporated herein by this reference, I have disclosed a dialyzer designed to be used frequently for short periods of time and which may be discarded after use. The design eliminates the need for a blood pump and also avoids the requirement of complex associated equipment and safety circuits In particular, the apparatus of the invention of my U.S. Pat. No. 3,788,482 is adapted for use under a program of daily dialysis at home so as to provide a more nearly continuous removal of poisons from the blood and thus avoid the increased buildup of blood contaminates that occur with less frequent treatment.

However, the folded membrane dialyzer of my U.S. Pat. No. 3,788,482 requires a multi-element or form in place case that is relatively expensive to fabricate. In the invention of my U.S. Pat. No. 3,788,482, end edges and side edges of the folded membrane are sealed by encapsulation in a plastic material that forms a portion of the housing. Access ports for blood and dialysate are formed by removal of studs that are positioned during curing or solidification of the sealing plastic. In the invention of my U.S. Pat. No. 3,788,482, the end edges of the folded membrane are positioned between support strips and encapsulated as a sub-assembly step before the stack is mounted to the remaining portions of the case. Alternatively, the case and edge encapsulation are formed in place about the folded membrane stack.

Accordingly, it is an object of the present invention to provide dialysis that eliminates or minimizes problems of the prior art and further eliminates or minimizes problems remaining with my prior invention.

SUMMARY OF THE INVENTION In carrying out principles of the present invention in accordance with a preferred embodiment thereof, a membrane having a pair of surfaces, end edges and side edges is folded into a stack of accordian pleated folds. Liquid flow enabling spacers are positioned between adjacent folds of the stack in contact with one of the membrane surfaces-An end fold plate is positioned upon each end edge of the membrane and the folded stack assembly is positioned within a preformed case having appropriate liquid flow ports and encapsulation injection channels. The case configuration cooperates with the end fold plate to facilitate encapsulation of the end and side edges of the folded membrane and, further, to block flow ofliquid encapsulation material into the liquid flow ports. The end folds of the stack of folds are positioned relative to the end fold plates so that upon injection of the encapsulation material through the encapsulation channels, the end edges of the folded membrane, for their entire length and including the side edges thereof, are completely embedded in the encapsulation material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a dialyzer embodying principles of the present invention;

FIG. 2 is an exploded view of FIG. I with one part of the case removed;

FIG. 3 is a cross section of the dialyzer of FIG. 1;

FIG. 4 is an enlarged fragmentary view of the section of FIG. 3;

FIG. 5 is a cross section showing ports of the dialyzer;

FIG. 6 is a cross section showing an end portion of the dialyzer of FIG. 1;

FIG. 7 is a horizontal section showing various elements of the dialyzer of FIG. 1 with parts broken away;

FIG. 8 is a vertical section of the dialyzer of FIG, 1;

FIG. 9 is a schematic perspective of the dialyzer, with parts broken away, and elements simplified to illustrate the flow paths;

FIG. 10 illustrates a dove-tailed form of modification of the end fold plates;

FIGS. 11 through 13 show still another modification of end fold sealing;

FIG. 14 illustrates a further modification of an end fold sealing arrangement;

FIG. 15 shows a further modification of an end fold sealing arrangement;

FIG. 16 illustrates a modified form of split housing;

FIG. 17 illustrates still another form of split housing for the dialyzer of the present invention; and

FIG. 18 shows still another form of end fold plates.

DETAILED DESCRIPTION Referring to FIGS. 1 through 8, a dialyzer embodying the principles of the present invention includes a case 10 having first and second case sides 11a, 11b, a top 13a, a bottom 13b and first and second case ends 16a, 16b. Although the terms top and bottom are employed to designate specified portions of the case, these terms do not imply or identify any preferred or required orientation of the dialyzer in use. It will be readily understood that the described apparatus may be used with any one of the sides, top and bottom, in upper position or with either of the ends in upper position.

The case is conveniently made of two substantially identical vacuum formed half sections, each having a continuous peripheral flange 15 having semicircular depressions 17a through 1711, mating with corresponding depressions in the other case half section to form encapsulation material injection channels 18a through 1812, that are used as described below. Integrally formed in the case sections are flow ports 20, 21, 22 and 23, each having a diminishing cross section (see FIG. 5) as the ports approach the case bottom 13b and respectively having flow connecting fittings 24, 25, 26, 27 extending through the casing top 13a and bonded to the ports at the points thereof of maximum cross section. When the case is formed by injection molding, the fittings may be integral with the ports. Both casing sides are formed with enlargements 28, 29, 30, 31 (as best seen in FIG. 7) at points adjacent the case ends and include rebated portions 32, 33, 34, 35 (relative to enlargements 28, 29, 30, 31) formed between the enlarged side portions 28, 29, and the flow ports.

The top and bottom of the case are also formed with enlarged portions (FIGS. 2, 5, 8) identified at 37, 38, 39, 40. For reasons that will appear from the ensuing description, the enlargements of the case sections at the ends thereof are required only as enlargements of the interior of the case at the identified areas. Exterior enlargement is not required. Nevertheless, because of the mode of the forming of the case sections, vacuum forming in a preferred embodiment, it is most convenient to form the ends of the case sections with outwardly projecting walls that inherently form the described enlargements of the case interior. Therefore, when enlargements of the case are referred to herein, the primary reference is to the functional enlargement of the case interior.

Although vacuum forming of the case is described as a method of manufacture that is preferred because of lower initial costs of tooling, it will be readily appreciated that the case sections may be made by other means such as for example, injection molding. Where other methods of manufacture are used, the various elements of the case, the ports, the injection channels, connection flanges and enlargements, may be formed by those related methods that are more readily adaptable to the specific manufacturing processes. Nevertheless, regardless of the method of manufacture chosen, the interior dimensions and configurations of the case will be as described herein with regard to the exemplary vacuum formed embodiment, and these will achieve the improvements deriving from the present invention.

Mounted within the case 10 is an edge sealed folded membrane stack assembly 41 (FIG. 2) that is arranged to provide a number of fluid-flow channels. The arrangement is such that all flow channels in contact with one surface of the membrane are in communication with each other. The two sets of channels are sealed and isolated each from the other. As illustrated in FIGS. 3, 4 and 9, the folded membrane stack assembly comprises a sheet of a semipermeable membrane, initially in an exemplary rectangular configuration, having end edges, side edges, and opposite surfaces. The membrane is preferably formed of cellophane having a thickness of0.0006 inches, a widely available, inexpensive and effective dialysis material. Nevertheless, other semi-permeable membranes known in the art may be employed without departing from principles of this invention. The membrane is folded into the configuration illustrated in FIGS. 2, 4 and 9 in a stack of accordian pleats, providing a plurality of folds such as folds 42a, 42b, 42c and 42d. The stack includes a first or top end fold 44 that terminates in a first end edge 45 of the membrane, and a second or bottom end fold 46 terminating in a second end edge 47 of the membrane. The folds of the stack reverse their direction at fold edges such as 48a, 48b, on one side of the stack, and fold edges 49a, 49b, etc., on the other side, which collectively form sides of the stack.

In the exemplary arrangement illustrated in the drawings, each end fold 44, 46 extends in the same direction, from the right side of the stack as viewed in FIG. 4 to an intermediate portion of the stack. The stack includes pleats or channels that comprise first and second groups of channels for the juxtaposed flow of the two fluids. FIG. 9 shows the arrangement of the invention with simplified parts and illustrates the relative positioning of major components that allow the desired flow patterns. In this drawing, flow of contaminated fluid(blood) is indicated by the dashed lines (arrows B) and flow of contaminated absorbing fluid (dialysate) is indicated by solid flow lines (arrows D). All of the channels of the first group of channels open to the left as viewed in FIG. 4 and are formed between adjacent folds defined by a single surface of the folded membrane. All channels of the second group open to the right as viewed in FIG. 7, and all are formed by the other surface, between adjacent folds, of the membrane. Solely for convenience of exposition, and not by way of limitation, the first group of channels, those opening to the left, may be termed dialysate channels since these will direct flow of a cleansing fluid such as a dialysate, while the second group of channels, those opening to the right, may be termed the blood channels since a fluid containing contaminates or other elements to be removed, such as blood, flows through these. Within each of the dialysate channels is a liquid flow enabling spacer or support member preferably formed of a plastic, non-woven mesh that will maintain a suitable spacing between adjacent folds and yet provide a minimum impediment to flow of dialysate through the channels. Such non-woven mesh has two layers of threads, each layer being in a different plane. These spacer members (not shown in FIG. 9) are identified in the drawings by reference numerals 50a, 50b, etc.

Preferably, no spacer members are inserted between adjacent folds of the blood channels wherefor such adjacent folds are substantially in contact each with the other until a pressurized liquid is caused to flow therethrough. In some cases, spacer members may be used between all folds of both groups of channels, particularly if the higher pressure fluid does not act to open the higher pressure channels.

inserted between end fold 44 at one end of the stack and the next adjacent inner fold 42a, is an end fold plate 52. Similarly, at the other end of the stack an end fold plate 54 is inserted between the end fold 46 and the next adjacent inner fold 4211. The end fold plates are identical to each other, each comprising a substantially rigid plastic support and positioning strip 55 and a pair of mutually spaced shoulders or liquid flow blocking strips 56, 57 that are bonded to support strip 55 to define a channel 58 therebetween. End fold 44 extends around the end fold plate over and around the blocking strip 56 and terminates at a point intermediate the sides, top and bottom of channel 58. The end portion of the end fold including end edge 45 is positioned within the channel by means of first and second end fold spacers or sealer spacers 59, 60 that extend across the full width and length of the channel 58 on opposite sides of the end portion of end fold 44. The end fold spacers are conveniently formed of the same nonwoven mesh material as are spacers 50a, 50b, etc. End fold spacers 59, 60 position the end edge and an outer portion of the end fold relative to the end fold plate so as to provide sealing spaces between the end fold and the surface of positioning strip 55 and also between the outer portion of the end fold and the adjoining inner surface of the case, as best seen in FIG. 4. Preferably, the mutually facing edges of blocking strips or shoulders 56, 57 are slightly inclined as indicated at 64, 65 to enhance retention of of end fold spacers 59, 60.

Each plate or support and positioning strip 55 may be a rigid plastic bar of a width equal to the width of the stack and a length slightly less than the length of the stack for reasons to be described below. Shoulders 56, 57 are conveniently formed as polycarbonate, polyure thane, polyvinyl or the like or foam strips bonded to the flat plastic bar 55 so as to cooperate therwith to define the channel or groove 58 for reception of encapsulating solidifiable fluid as will be described below.

For assembly of the dialyzer, the folded assembly of accordian pleated membrane, spacer strips and end fold plates is slightly compressed in a vertical dimension as viewed in FIG. 4, and inserted into the two case halves after the inner surfaces of the sides 11a, 11b thereof have been coated with a suitable thixotropic encapsulating material for substantially the entire length of the casing sides between the flow ports 20, 21 and between the flow ports 22, 23. The rigidity of the nearly full length end fold plates 52, 54 completes a sub-assembly of membrane folds and mesh spacers that is readily handled. The encapsulating material coating that is placed on the interior of the case sides prior to positioning of the folded stack assembly in the casing section is indicated at 66 and 68 in FIG. 3. The confronting or contiguous surfaces of flanges 15 are coated with a solvent or other bonding agent prior to mounting of the stack assembly within the casing sections so that when the two case sections are pressed against one another, the flanges are bonded to each other to fix the two case sections together. Other arrangements may be used to bond the flanges, including clamping devices. ultrasonic welding and thermal welding.

Encapsulating material 70 is then injected into the interior of the casing through the encapsulation channels 18a through 1811 (FIG. 1). Because of the configuration and positioning of the end folds, end edges and side edges in relation to the interior of the case. all edges of the folded membrane are fully and completely encapsulated by the injected material, and the laterally outwardly directed openings of the blood and dialysate channels at the fold edges of the stack are also embedded in the encapsulating material at the inner surface of the case sides. Therefore, one surface of to folded membrane is fully and completely sealed from and isolated from the other surface.

The one surface as folded forms a number (such as 60 for example) of blood channels each communicating at one end with a first flow port, such as port 20, and each communicating in common at a second end to a second flow port, such as flow port 21. The dialysate channels formed by the opposite surface of the membrane all communicate in common with a flow port, such as 22, at one end of each channel and with another flow port such as 23 at the other end of each channel. Note that the encapsulating material 66, 68 on the inner surfaces of case sides 11a, 11b, does not extend to the flow ports and thus, each of the channels that opens to a respective flow port remains open at the area of the flow port.

The encapsulating material is liquid when injected and has a relatively high viscosity to enable it to flow through the channel injection ports and over and around edges of the membrane. Because of its thixotropic properties, the material does not penetrate any significant distance into the channels between adjacent pleats. The liquid material solidifies in place and accordingly provides a full and complete encapsulation of all end edges and side edges of the membrane. A wide variety of encapsulating materials may be employed without departing from principles of the invention but the material chosen must be inert to blood since it will be in contact with the blood in the blood channels. The encapsulating material readily flows when liquid and is capable of rapid solidification, remaining solid at room temperature. Examples of substances that can be used for encapsulation include polycthelene, polypropylene, polycarbonate, epoxy resins, polyester resins, polystyrene and the like.

A particular example of a plastic material formulation which has been successfully used in parts of EPON 828, a diglycidyl ether of bisphenyl A epoxy resin produced by Shell Chemical Company, l0 parts of triethelenetetramine which acts as a curing agent, and 10-12 parts of a thickening agent Cab-O-Sil which is a silica aerogel produced by Cabot Corporation. Still 7 other materials are mentioned in my copending application, Ser. No. 233,528.

Illustrated in FIG. 4 is a significant feature of the end edge sealing arrangement that permits use of preformed flow ports which remain unaffected by flow of the encapsulating material during its injection. As particularly illustrated in this figure, the blocking strip 56 in conjunction with blocking strip 57 forms an encapsulating material channel 58, which receives and confines the encapsulating material as it is injected in its liquid state. Because of the close and contiguous juxtaposition of the facing surfaces of the blocking strips 56, 57 and the adjacent inner surface of the top of the case top 13a, the liquid encapsulating material cannot flow to the case sides 11a, 11b, and thus will not flow down over the fold edges at the portions thereof that must be open to the flow ports 20, 21, 22, 23. The same is true for the blocking strips at the case bottom 13b.

In order to insure and facilitate encapsulation of the side edges of the membrane, each end fold plate is made of a length less than the width of the membrane so that the edges 43 of the latter will extend beyond the edge 51 of the end fold plates 52, 54 as illustrated in FIGS. 7, 8 and 9. Further, the length of the case (FIG. 7) is somewhat greater than the total width of the membrane so that the side edges 43 of the folded membrane will be spaced from the inner surface of the case ends 16a, 16b.

In order to insure flow of the liquid encapsulating material over the outermost surfaces of the side edges 43 of the end folds 44, 46 of the membrane, the interior of the case top and bottom at the case ends is enlarged as at 37, 38 in FIG. 8. Thus, the encapsulating material 70 can flow over and around both surfaces of the side edges of the folded membrane.

As illustrated in FIGS. 6 and 7, case sides 11a, 11b are enlarged at 28, 29, at the end portions thereof to provide additional space for flow of encapsulating material around the ends of the membrane fold edges, thus insuring a complete sealing of the membrane side edges. Portions such as 32, 33 (in FIG. 7) of the case between the enlarged case side ends 28, 29 and ports 20, 22 are a snug fit against the membrane fold edges. This further assists in blocking the flow of liquid encapsulating material from the end portion of the case to the flow ports. The viscosity of the injected encapsulating material is such that it will flow only a short distance into the stack folds between adjacent side edges, extending from the end of the case inwardly of the end of the end fold plate by a short distance toward the outermost wall of the flow ports. Thus, it will be seen that the end fold plates provide encapsulation and sealing of the end edges of the folded membrane while preventing blockage of the communication path between the several channels and flow ports. The configuration and relative spacing and positioning of case end enlargements, membrane side edges and ends of the end fold plate insure sealing of side edges of the membrane to thereby seal the ends of the several flow channels.

In operation of the dialyzer described herein, and as best shown in FIG. 1, and 9, one of te two liquids employed in the dialysis is introduced into a first port 21 and flows along the side of the stack for the length of the port. The decreasing cross section of the port insures proper distribution of the liquid, blood for example, into all of the blood channels. Improved distribution into all of the channels is accomplished since resistance to flow increases as the cross section of the port narrows and, concomitantly, resistance to flow is minimum at the portion of the port near the blood entrance that is of greater cross section. Thus, flow into all of the blood channels is provided and flow continues between and along each of the flat blood channels to the end of the channels which are in communication with flow port 20. Similarly, and concomitantly, a counterflowing dialysate is introduced into port 22 of which the tapering cross section optimumly distributes the dialysate to all of the dialysate channels. The counterflow is preferred, but not required. These channels. like the blood channels, also extend across the full width of the stack between case sides 11a and 11b, but are formed by the opposite surface of the membrane. The dialysate flows through the membrane channels, substantially the full length of the case to port 23 from which it is collected for regeneration or disposal.

The operation and pressures are as described in my copending application Ser. No. 233,528. Blood is introduced into the blood inlet port, with or without pumping, at approximately arterial pressure or higher, and thus separates the closely adjacent sides of the blood channels. Dialysate is introduced into the dialysate inlet port at a slightly lower pressure. In a well-known operation, the unwanted accumulations in a higher concentration in the blood pass through the membrane to the dialysate which has a lower concentration of such contaminates. Water also passes through the membrane because of the pressure difference across the membrane.

Illustrated in FIG. 10 is a modified form of end fold plates. In the arrangement of FIG. 10, the end fold plate (the plates at top and bottom of the stack are mutually identical) is made of a single integral strip having a longitudinally extending dovetailed groove 82 formed therein. End fold 44 and end fold sealer spacers 59, 60 are mounted to the end fold plate within the dovetailed groove or channel 82 just as in the arrangement heretofore described. The assembly and encapsulation operation of the arrangement of FIG. 10 is also exactly like that previously described.

Still another form of end fold plate is illustrated in FIGS. ll, 12 and 13 wherein the plate 84 is formed with a plurality of protruberances 85 on one surface thereof as by forming a network of corrugations or grooves. These protruberances on plate 84 cooperate with similar protruberances or linear corrugations 86, 87 formed on the inner surface of outwardly projecting portions 88, 90 of the tops of the casing sections. The tops include rebated portions 92, 94 that are in close abutting fit against outer portions of the end fold plate on opposite sides of the case. A portion of end 44 is interposed between the end fold plate 84 and the rebated portion 92 of the case top. In this arrangement, the cooperating protruberances on the case top and end fold plate perform the function of the sealer spacers of the previously described embodiment to position the end fold together with its end edge and form sealing spaces on opposite surfaces thereof for reception of a freeflowing solidifiable encapsulation material. This provides edge sealing as is described in connection with the previously mentioned embodiments. The arrangement of plate, end fold, spacers and case is the same at the bottom of the case. In the embodiments of FIGS. 11 through 13, and also in the embodiment of FIG. 10, the end fold plates are made somewhat shorter than the full width of the folded membrane just as descirbed in connection with the first embodiment.

Illustrated in FIG. 14 is still another modification of the end fold edge sealing employing a case having outwardly projecting portions 98, 100 formed on the top of the case sections and having rebated portions 101, 102 that cooperate with an end fold plate 104, to block flow of liquid encapsulating material toward the case sides 111a, lllb. The end fold plate 104 is formed as a flat bar of plastic inserted between the end fold and the next adjacent inner fold. The end fold plate is positioned in close contiguity with the inner surface of the case section top at portions 101, 102 thereof and the end fold 44c has an end portion 44d that is angulated with respect to the rest of the end fold and extends into the projecting case section top portions 98, 100. Mesh sealer spacer strips 105, 106 are positioned on opposite sides of the end portion 44d of the end fold so that liquid encapsulation material injected through the case top will flow over, through and around the mesh sealer spacers to fully encapsulate both surfaces of the end fold. Again, as in previously described embodiments, the end fold plate 104 has a length less than the width of the folded stack to allow the side edges of the latter to protrude beyond the ends of the plate 104 thus improving side edge encapsulation.

As shown in FIG. 15, the arrangement of FIG. 14 may be modified to provide a slightly extended outwardly projecting portion 108, 110 of the top of the case sections and rebated portions 112, 113 in close contiguity with outer portions of an end fold plate 115 having the end fold 44e interposed between portions 112, 113, and strip 115. The end fold 44e has an end portion 44fthat is spaced from the case section top 110 and from the end fold plate 115 by mesh spacer strips 116, 117 that are in contact with opposite surfaces of end fold end portion 44f The end fold plate 115, like the end fold plate 104, FIG. 14, is made as a thin, flat, rigid plastic bar having an extent less than the width of the folded membrane to allow the side edges of the membrane to extend beyond the end fold plate for improved side edge encapsulation. Encapsulating material, as in previously described embodiments, fills the sealer spaces between the case section top 108, 110 and the end fold plate 115, flowing through the spacers 116, 117 upon both surfaces of the end fold.

Other arrangements for encapsulating the end edge of the end fold may be employed without departing from principles of the present invention, bearing in mind that each arrangement should provide a configuration, in addition to facilitating handling, that will block flow of the liquid encapsulating material to the ports and to those portions of the blood and dialysate channels that are in communication with the flow ports. End fold sealing is the same at top and bottom of the case in the arrangements of each FIGS. 14, 15 and 16.

The end fold plates 52, 54 perform two separate functions. The first of these, which is of importance in handling and assembly of the apparatus, derives from the fact that the two rigid end fold plates are positioned on either side of a stack of membrane folds and thus stiffen and support the stack together with the interleaved mesh spacers before the stack is inserted in the case. The rigid strips enable the fragile membrane and mesh spacer stack to be maintained in a somewhat compressed (as when grasped by a hand, for example) rectilinear configuration so that it may be readily moved about, handled and inserted into the one case half, and further, so that the second case half may be inserted over and about the stack. 5 The second major function of the end fold plates in some ofthe described configurations is to prevent flow of the liquid encapsulating material into the ports through 24. For this function, the plate need not extend the full length of the assembly, but need extend only for a short distance from its ends, adjacent to the casing end, to a point somewhat inwardly (in the longitudinal direction of the case) of the inward side of the ports. Nevertheless, in order to obtain the advantages of improved handling of the stack, the end fold plates are made as unitary rigid strips extending nearly the full length of the stack.

Still another arrangement for blocking flow of liquid encapsulating material into the ports may be achieved by direct contact of an inwardly rebated portion of each corner of the top and bottom of the case which presses directly upon the respective corner of the end fold and next adjacent inner fold of the folded stack. To allow such direct contact between the case top and bottom at the corners thereof with the membrane folds at portions of the case adjacent the ports and the corresponding corners of the outermost mesh spacers are removed. Thus, the blocking function is achieved by direct contact of the case with the membrane while the handling function of the end fold plates, which now perform little or no sealing function, is still available.

In the arrangement described above, the end fold 44 on either side of the stack is the outermost element of at least one part of the stack on both the top and bottom. Since the material of which the membrane is made is fragil and may be accidently torn or otherwise disturbed during handling or insertion into the case, it may be desirable to afford some protection for even this end fold on both sides of the stack. To this end, the arrangement shown in FIG. 18 may be employed wherein each end fold plate is made of two nearly identical and facing sections 54a, 54b, each having a channel, but with the two channels facing each other as illustrated. The outer of the two sections, 54b, is formed with a series of apertures'such as that indicated at 540, in alignment with the liquid encapsulation material injecting channels, such as that designated 118b, of which a series are formed in the top and bottom of the case as previously described. In this arrangement, the end fold 44a extends around the inner section 54a of the split end fold plate and terminates in the space formed by the mating grooves of the upper and lower sections 54a and 54b. Thus, the end fold 44a is fully and completely protected by the outer end fold plate section 54b during assembly and during handling before insertion into the case. Liquified encapsulation material is injected through the channel 11812, and through other similar channels, and through the plurality of the registering apertures 540 in the upper end fold plate section to flow into the space formed by the mating grooves and through and along the mesh spacers that are also positioned as previously described within the groove on either side of the end fold 44a. The arrangement on the other end of the stack may be identical to that shown in FIG. 18.

Although the preferred arrangement of the case employs two substantially identical sections for economy of manufacture, it will be readily appreciated that the case may be made in shapes other than rectangular in section for example, and in two or more than two nonsymmetrical sections. lllustrated in FIG. 16 is an arrangement wherein the case is formed by a first section 120 that includes both top and bottom and one side of the case and a second section 122 forming but a single side of the case and including the two flow ports formed in such sides. Suitable flanges 123a, b, c and d, are formed in the two case sections for bonding of the sections together so as to confine and position a folded membrane stack, exactly as previously described.

An alternate configuration of a case employing identical symmetrical sections is illustrated in H0. 17 as comprising triangular cross section case halves 125, 127, each having mating flanges 128a, b, c and (1 to fix the two case sections to each other with the previously described folded membrane stack assembly confined therein. Tapered cross-section blood ports and encapsulating material injecting channels (not shown) are formed in the case sections of FIGS. 16 and 17 in a manner similar to those in previously described embodiments.

ln the arrangements described herein, the use of barrier sheets and studs or other devices to maintain communication between the several channels and the flow ports is not required. Further, the entire folded assembly can be pre-assembled in a totally dry condition including folded membrane, end fold plates and the several sealer spacer strips, requiring no adhesive, encapsulation material nor curing time. The assembly may be positioned dry within the casing sections of which the sides have been previously coated with encapsulation material or with a closed cell sponge, a soft rubber sheet, or a gel sheet, these materials not requiring cure and which may not require liquid application. However, these arrangements result in loss of the case stiffening effect of bonding membrane fold edges to the case sides. The encapsulation material is then injected into the case as needed and only one period of cure or solidification time is necessary, greatly minimizing the cost, effort and complexity of manufacture and assembly.

In a preferred configuration employing a membrane with 60 folds, the case dimensions are approximately I-% inches wide by l-% inches high by ll inches long and the width of the ports (in the longitudinal direction of the case) is between V8 and /2 inch. The relatively small ratio of channel width to length and the input flow velocities provided by the preferred port width, achieve improved flow distribution over the surface area of the membrane.

Although the invention has been described in a form particularly adapted for use as a hemodialyzer, it will be readily appreciated that it may be employed for filtering other fluids or liquids, flowing other types of contaminated fluid through the blood channels and flowing other types of cleansing solution through the dialysate channels or effecting different types of transfer between particular fluids. Of course, other encapsulation materials compatible with the particular membrane and case material will be chosen from those materials that exhibit proper flow characteristics and which may be conveniently solidified. Accordingly, the terms blood" and dialysate as employed herein to identify liquids, channels and ports, are used merely for convenience of exposition and are to be construed as including other fluids. Also other types of membranes or folded sheets may be employed as dictated by the particular fluids and by the nature of the desired transfer between the fluids.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

What is claimed is:

1. Fluid flow transfer apparatus comprising a membrane having first and second surfaces, first and second end edges, first and second side edges, said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides of a first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack, said stack including a plurality of fold edges collectively forming opposite sides of the stack,

a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds, first and second case ends extending along the respective side edges of te folded membrane, said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges,

a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces,

means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top and at a distance from an adjacent membrane fold to provide first and second end edge sealing spaces on oppostie surfaces of said end fold,

a solidified fluid material within said first and second sealing spaces encapsulating said one end edge, and means for blocking flow of said fluid material from said first and second sealing spaces to said flow ports of said case sides.

2. The apparatus of claim 1 wherein said means for positioning said one end fold comprises an end fold plate positioned on one end of the stack between said end fold and an adjacent inner fold of said membrane, a first sealer spacer positioned between one surface of said end fold and said plate, a second sealer spacer positioned at the other surface of said end fold, and wherein said means for blocking flow from said first and second sealing spaces comprises first and second mutually spaced shoulders positioned adjacent first and second sides of said stack and said case top.

3. The apparatus of claim 2 wherein said shoulders comprise first and second blocking strips mounted along mutually opposed sides of said plate to define a channel running along said plate between the sides of the stack, said one end edge and said first and second sealer spacers being positioned within said channel, said solidified fluid material substantially filling said channel between said plate, said blocking strips and said case top.

4. The apparatus of claim 2 wherein said plate and shoulders are formed integrally of a substantially rigid bar, said channel being formed as a dove-tailed groove cut in one surface of the bar and extending longitudinally thereof intermediate its sides, said one end edge terminating intermediate the walls of said dove-tailed groove, and said first and second sealer spacers extending on opposite sides of said end fold for substantially the full length and width of said dove-tailed groove.

5. The apparatus of claim 2 wherein the side edges of said folded membrane extend beyond the ends of said end fold plate and further including solidified material encapsulating the side edges of said membrane and extending between said side edges and said case top and bottom, and extending over both surfaces of said membrane at said side edges including the outermost surface of the end folds of said stack, the end folds of said stack extending over said shoulders between the shoulders and the case top and bottom.

6. The apparatus of claim 1 wherein said case top is formed with an outwardly projecting portion intermediate the case sides, at least one of said first and second sealer spacers being positioned within said outwardly projecting case top, and wherein said means for blocking flow from said sealing spaces to said flow ports comprises an inwardly rebated portion of said case top at the outer side edges of said case top in contiguous juxtaposition to outer side portions of said plate, the space between said sealer strip and said outwardly projecting case top portion being substantially filled with said solidified material.

7. The apparatus of claim 6 wherein said end fold terminates in a portion that is angulated with respect to the plane of the membrane folds.

8. The apparatus of claim 6 wherein the outermost portion of said end fold extends in a direction substantially parallel to the folds of said stack and is spaced from said plate and said casing top by sealer spacers positioned upon respectively opposite surfaces of said end fold.

9. The apparatus of claim 1 wherein said case top is formed with an outwardly projecting portion intermediate the casing sides, and wherein said means for positioning a portion of at least one of said end folds comprises an end fold plate between said end fold and an adjacent inner fold, a plurality of protuberances on mutually facing surfaces of said plate and said case top projecting portion, and wherein said means for blocking flow comprises an inwardly rebated portion of said case top at outer edges thereof in contiguous juxtaposition to outer side portions of said plate.

10. The apparatus of claim 1 wherein the interior of the case is enlarged at the ends of said top and bottom walls to provide a space to receive encapsulating material between outermost surfaces of said end folds and said enlarged case ends.

11. The apparatus of claim 1 wherein the interior of the case is enlarged at end portions of said case sides and wherein encapsulating material is positioned between said enlarged case sides and the stack fold edges at ends of said case thereby to effect edge encapsulation around said side edges.

12. The apparatus of claim 1 wherein at least one of said ports is formed as a port enlargement of a portion of the case side at a point spaced from the case end, said case side having a portion in close juxtaposition to the fold edges of said stack between said one port and said enlarged case side wall.

13. The apparatus of claim 12 wherein said port enlargement has a cross section that decreases along the height of said stack and includes a port connection in communication with the port at a portion thereof having a relatively large cross section.

14. The apparatus of claim 1 wherein said case includes a plurality of encapsulating liquid injection channels extending through the walls thereof and communicating with the interior of the case.

15. The apparatus of claim 14 wherein said case is formed of first and second mating integral case sections having conjoining securing flanges, said encapsulating liquid injection channels being jointly defined by mating grooves formed in adjoining portions of the flanges of said first and second sections.

16. The method of making a fluid flow apparatus comprising the steps of folding a membrane having first and second surfaces,

first and second end edges, and first and second side edges into a stack of accordian pleated folds having fold edges defining sides of the stack and having first and second end folds on the top and bottom of the stack, and terminating at said end edges intermediate said stack sides,

positioning flow enabling spacers between adjacent folds of said stack in contact with at least one surface of said membrane, positioning an end fold plate at each end fold, positioning portions of said end folds including said end edges at a distance from an intermediate portion of said end fold plate, inserting said stack together with said end fold plates into a case,

injecting a solidifiable encapsulating material through said case to encapsulate both said end edges and both said side edges of said membrane along both said surfaces thereof, allowing said injected material to solidify, and

blocking flow of said material toward the fold edges of said stack and toward outer sides of said case during solidification of said injected material.

17. The method of claim 16 wherein said step of inserting the stack includes the step of positioning surfaces of said membrane at outer sides of said end fold plates in close contiguity with inner surfaces of said case, wherein said step of blocking flow of material toward the fold edges comprises the step of maintaining said end fold plate in closely contiguous relation to said case during solidification of the injected material, and wherein said step of positioning the end fold plate comprises positioning the plate between each end fold and in adjacent inner fold.

l8. Fluid flow transfer apparatus comprising a membrane having first and second surfaces,

first and second end edges,

first and second side edges,

said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides of a first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack, said stack including a plurality of fold edges collectively forming opposite sides of the stack,

a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds,

first and second case ends extending along the respective side edges of the folded membrane,

said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges, a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces, means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top to provide an end edge sealing space for said end fold, a solidified fluid material within said sealing space encapsulating said one end edge, said case being enlarged at the ends thereof to provide spaces for receiving said fluid material between the case and the stack whereby said fluid encapsulating material may readily flow to and be received about side edges of the stack. 19. The apparatus of claim 18 wherein said enlargement of the case end includes an enlargement of the interior of the case at the ends of the top and bottom of the case to receive said fluid material between the top of the case and the outer surface of the side edge of the membrane end fold.

20. The apparatus of claim 18 wherein a substantially rigid end fold plate is positioned between each end fold and an adjacent inner fold of the membrane, said plate extending for a major portion of the width of said case and stack to thereby facilitate handling of the subassembly of folded membrane and spacer members.

21. The apparatus of claim 20 wherein said case enlargement includes enlargements of the case sides at the ends thereof, said case sides including rebated portions in abutting relation with the sides of the stack between the flow ports and the enlarged portions of the ends of the case sides.

22. The apparatus of claim 20 wherein said case includes a plurality of encapsulation material injection channels, and wherein said end fold plate includes first and second plate sections having elongated face-toface grooves formed therein, one of said elongated plate sections having a plurality of apertures formed therethrough in communication with the grooves of the plate sections and in communication with said injection channels, said end folds each being sandwiched between said first and second plate sections and having an end edge terminating within said grooves, and first and second spacer sealer members positioned between said end fold end edges and opposite sides of the mating grooves of said plate sections.

23. Fluid flow transfer apparatus comprising a membrane having first and second surfaces, first and second end edges, first and second side edges, said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides ofa first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack,

said stack including a plurality of fold edges collectively forming opposite sides of the stack,

a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds, first and second case ends extending along the respective side edges of the folded membrane, said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges,

a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces,

means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top to provide an end edge sealing space for said end fold,

a solidified fluid material within said sealing space encapsulating said one end edge. and

first and second rigid end fold plates extending substantially the full width of said positioned respectively between each end fold and an adjacent inner fold of the membrane, each said plate terminating at a point short of the side edge of the folded membrane whereby the subassembly of folded mem brane, spacer members and rigid plates may be readily handled and inserted into the case and whereby the side edges of the end folds which extend beyond the rigid plates are free to be encapsulated by said fluid material.

24. The apparatus of claim 23 wherein said case includes top, bottom and first and second sides at least some of which are outwardly enlarged to provide a space between the stack and the case for receiving encapsulating fluid material to enhance encapsulation of the side edges thereof.

25. The apparatus of claim 23 wherein the interior of the case is enlarged at the ends of said top and bottom walls to provide a space to receive encapsulating material between outermost surfaces of said end folds and said enlarged case ends.

26. The apparatus of claim 23 wherein the interior of the case is enlarged at end portions of said case sides and wherein encapsulating material is positioned between said enlarged case sides and the stack fold edges at ends of said case thereby to effect edge encapsulation around said side edges.

27. The apparatus of claim 23 wherein at least one of said ports is formed as a port enlargement of a portion of the case side at a point spaced from the case end, said case side having a portion in close juxtaposition to the fold edges of said stack between said one port and said enlarged case side wall.

28. The apparatus of claim 23 wherein said case includes a plurality of encapsulation material injection channels, and wherein said end fold plates each includes first and second plate sections having elongated face-to-face grooves formed therein, one of said elongated plate sections having a plurality of apertures formed therethrough in communication with the grooves of the plate sections and in communication with said injection channels, said end folds each being sandwiched between said first and second plate sections and having an end edge terminating within said grooves, and first and second spacer sealer members positioned between said end fold end edges and opposite sides of the mating grooves of said plate sections. 

1. Fluid flow transfer apparatus comprising a membrane having first and second surfaces, first and second end edges, first and second side edges, said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides of a first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack, said stack including a plurality of fold edges collectively forming opposite sides of the stack, a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds, first and second case ends extending along the respective side edges of te folded membrane, said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges, a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces, means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top and at a distance from an adjacent membrane fold to provide first and second end edge sealing spaces on oppostie surfaces of said end fold, a solidified fluid material within said first and second sealing spaces encapsulating said one end edge, and means for blocking flow of said fluid material from said first and second sealing spaces to said flow ports of said case sides.
 2. The apparatus of claim 1 wherein said means for positioning said one end fold comprises an end fold plate positioned on one end of the stack between said end fold and an adjacent inner fold of said membrane, a first sealer spacer positioned between one surface of said end fold and said plate, a second sealer spacer positioned at the other surface of said end fold, and wherein said means for blocking flow from said first and second sealing spaces comprises first and second mutually spaced shoulders positioned adjacent first and second sides of said stack and said case top.
 3. The apparatus of claim 2 wherein said shoulders comprise first and second blocking strips mounted along mutually opposed sides of said plate to define a channel running along said plate between the sides of the stack, said one end edge and said first and second sealer spacers being positioned within said channel, said solidified fluid material substantially filling said channel between said plate, said blocking strips and said case top.
 4. The apparatus of claim 2 wherein said plate and shoulders are formed integrally of a substantially rigid bar, said channel being formed as a dove-tailed groove cut in one surface of the bar and extending longitudinally thereof intermediate its sides, said one end edge terminating intermediate the walls of said dove-tailed groove, and said first and second sealer spacers extending on opposite sides of said end fold for Substantially the full length and width of said dove-tailed groove.
 5. The apparatus of claim 2 wherein the side edges of said folded membrane extend beyond the ends of said end fold plate and further including solidified material encapsulating the side edges of said membrane and extending between said side edges and said case top and bottom, and extending over both surfaces of said membrane at said side edges including the outermost surface of the end folds of said stack, the end folds of said stack extending over said shoulders between the shoulders and the case top and bottom.
 6. The apparatus of claim 1 wherein said case top is formed with an outwardly projecting portion intermediate the case sides, at least one of said first and second sealer spacers being positioned within said outwardly projecting case top, and wherein said means for blocking flow from said sealing spaces to said flow ports comprises an inwardly rebated portion of said case top at the outer side edges of said case top in contiguous juxtaposition to outer side portions of said plate, the space between said sealer strip and said outwardly projecting case top portion being substantially filled with said solidified material.
 7. The apparatus of claim 6 wherein said end fold terminates in a portion that is angulated with respect to the plane of the membrane folds.
 8. The apparatus of claim 6 wherein the outermost portion of said end fold extends in a direction substantially parallel to the folds of said stack and is spaced from said plate and said casing top by sealer spacers positioned upon respectively opposite surfaces of said end fold.
 9. The apparatus of claim 1 wherein said case top is formed with an outwardly projecting portion intermediate the casing sides, and wherein said means for positioning a portion of at least one of said end folds comprises an end fold plate between said end fold and an adjacent inner fold, a plurality of protuberances on mutually facing surfaces of said plate and said case top projecting portion, and wherein said means for blocking flow comprises an inwardly rebated portion of said case top at outer edges thereof in contiguous juxtaposition to outer side portions of said plate.
 10. The apparatus of claim 1 wherein the interior of the case is enlarged at the ends of said top and bottom walls to provide a space to receive encapsulating material between outermost surfaces of said end folds and said enlarged case ends.
 11. The apparatus of claim 1 wherein the interior of the case is enlarged at end portions of said case sides and wherein encapsulating material is positioned between said enlarged case sides and the stack fold edges at ends of said case thereby to effect edge encapsulation around said side edges.
 12. The apparatus of claim 1 wherein at least one of said ports is formed as a port enlargement of a portion of the case side at a point spaced from the case end, said case side having a portion in close juxtaposition to the fold edges of said stack between said one port and said enlarged case side wall.
 13. The apparatus of claim 12 wherein said port enlargement has a cross section that decreases along the height of said stack and includes a port connection in communication with the port at a portion thereof having a relatively large cross section.
 14. The apparatus of claim 1 wherein said case includes a plurality of encapsulating liquid injection channels extending through the walls thereof and communicating with the interior of the case.
 15. The apparatus of claim 14 wherein said case is formed of first and second mating integral case sections having conjoining securing flanges, said encapsulating liquid injection channels being jointly defined by mating grooves formed in adjoining portions of the flanges of said first and second sections.
 16. The method of making a fluid flow apparatus comprising the steps of folding a membrane having first and second surfaces, first and second end edges, and first and second sIde edges into a stack of accordian pleated folds having fold edges defining sides of the stack and having first and second end folds on the top and bottom of the stack, and terminating at said end edges intermediate said stack sides, positioning flow enabling spacers between adjacent folds of said stack in contact with at least one surface of said membrane, positioning an end fold plate at each end fold, positioning portions of said end folds including said end edges at a distance from an intermediate portion of said end fold plate, inserting said stack together with said end fold plates into a case, injecting a solidifiable encapsulating material through said case to encapsulate both said end edges and both said side edges of said membrane along both said surfaces thereof, allowing said injected material to solidify, and blocking flow of said material toward the fold edges of said stack and toward outer sides of said case during solidification of said injected material.
 17. The method of claim 16 wherein said step of inserting the stack includes the step of positioning surfaces of said membrane at outer sides of said end fold plates in close contiguity with inner surfaces of said case, wherein said step of blocking flow of material toward the fold edges comprises the step of maintaining said end fold plate in closely contiguous relation to said case during solidification of the injected material, and wherein said step of positioning the end fold plate comprises positioning the plate between each end fold and in adjacent inner fold.
 18. Fluid flow transfer apparatus comprising a membrane having first and second surfaces, first and second end edges, first and second side edges, said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides of a first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack, said stack including a plurality of fold edges collectively forming opposite sides of the stack, a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds, first and second case ends extending along the respective side edges of the folded membrane, said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges, a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces, means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top to provide an end edge sealing space for said end fold, a solidified fluid material within said sealing space encapsulating said one end edge, said case being enlarged at the ends thereof to provide spaces for receiving said fluid material between the case and the stack whereby said fluid encapsulating material may readily flow to and be received about side edges of the stack.
 19. The apparatus of claim 18 wherein said enlargement of the case end includes an enlargement of the interior of the case at the ends of the top and bottom of the case to receive said fluid material between the top of the case and the outer surface of the side edge of the membrane end fold.
 20. The apparatus of claim 18 wherein a substantially rigid end fold plate is positioned between each end fold and an adjacent inner fold of the membrane, said plate extending for a major portion of the width of said case and stack to thereby facilitate handling of the subassembly of folded membrane and spacer members.
 21. The apparatus of claim 20 wherein said case enlargement includes enlargements of the case sides at the ends thereof, said case sides including rebated portions in abutting relation with the sides of the stack between the fLow ports and the enlarged portions of the ends of the case sides.
 22. The apparatus of claim 20 wherein said case includes a plurality of encapsulation material injection channels, and wherein said end fold plate includes first and second plate sections having elongated face-to-face grooves formed therein, one of said elongated plate sections having a plurality of apertures formed therethrough in communication with the grooves of the plate sections and in communication with said injection channels, said end folds each being sandwiched between said first and second plate sections and having an end edge terminating within said grooves, and first and second spacer sealer members positioned between said end fold end edges and opposite sides of the mating grooves of said plate sections.
 23. Fluid flow transfer apparatus comprising a membrane having first and second surfaces, first and second end edges, first and second side edges, said membrane being folded to form a stack of folds having a first end fold terminating at said first end edge intermediate the sides of a first end of the stack and having a second end fold terminating at said second end edge intermediate the sides of the other end of the stack, said stack including a plurality of fold edges collectively forming opposite sides of the stack, a case encompassing said stack and including first and second case sides extending along respective sides of said stack adjacent said end folds, first and second case ends extending along the respective side edges of the folded membrane, said case including a plurality of flow ports in said case sides in communication with said first and second membrane surfaces at said fold edges, a plurality of spacer members positioned between selected folds of said stack in contact with one of said membrane surfaces, means for positioning a portion of at least one of said end folds including the end edge thereof at a distance from the adjoining case top to provide an end edge sealing space for said end fold, a solidified fluid material within said sealing space encapsulating said one end edge, and first and second rigid end fold plates extending substantially the full width of said positioned respectively between each end fold and an adjacent inner fold of the membrane, each said plate terminating at a point short of the side edge of the folded membrane whereby the subassembly of folded membrane, spacer members and rigid plates may be readily handled and inserted into the case and whereby the side edges of the end folds which extend beyond the rigid plates are free to be encapsulated by said fluid material.
 24. The apparatus of claim 23 wherein said case includes top, bottom and first and second sides at least some of which are outwardly enlarged to provide a space between the stack and the case for receiving encapsulating fluid material to enhance encapsulation of the side edges thereof.
 25. The apparatus of claim 23 wherein the interior of the case is enlarged at the ends of said top and bottom walls to provide a space to receive encapsulating material between outermost surfaces of said end folds and said enlarged case ends.
 26. The apparatus of claim 23 wherein the interior of the case is enlarged at end portions of said case sides and wherein encapsulating material is positioned between said enlarged case sides and the stack fold edges at ends of said case thereby to effect edge encapsulation around said side edges.
 27. The apparatus of claim 23 wherein at least one of said ports is formed as a port enlargement of a portion of the case side at a point spaced from the case end, said case side having a portion in close juxtaposition to the fold edges of said stack between said one port and said enlarged case side wall.
 28. The apparatus of claim 23 wherein said case includes a plurality of encapsulation material injection channels, and wherein said end fold plates each includes first and second pLate sections having elongated face-to-face grooves formed therein, one of said elongated plate sections having a plurality of apertures formed therethrough in communication with the grooves of the plate sections and in communication with said injection channels, said end folds each being sandwiched between said first and second plate sections and having an end edge terminating within said grooves, and first and second spacer sealer members positioned between said end fold end edges and opposite sides of the mating grooves of said plate sections. 